Effect of photodynamic therapy on anti-tumor immune defenses: comparison of the photosensitizers hematoporphyrin derivative and chloro-aluminum sulfonated phthalocyanine.

The effects of the two photosensitizers chloroaluminum sulfonated phthalocyanine (ClAlSPc) and hematoporphyrin derivative (HpD) on the functional activities of macrophages and natural killer (NK) cells, two immunocyte populations implicated in the control of tumor development and spread, have been investigated. Murine peritoneal macrophages treated in vivo with ClAlSPc or HpD at 10 mg/kg body weight showed no impairment of Fc-mediated phagocytic capacity and only minor disturbances of in vitro tumoricidal/tumoristatic function. The NK cell activity of splenocytes obtained from photosensitizer-treated mice, assayed 24 or 48 h after i.v. injection of ClAlSPc or HpD at 10 mg/kg was unaffected compared to controls. However significant inhibition of NK activity was observed when splenocytes obtained from mice with or without subcutaneous Colo 26 tumors, treated with ClAlSPc plus laser therapy (675 nm) were used as effector cells. The results show that impairment of some anti-tumor activity can be observed in phthalocyanine treated or phthalocyanine + laser-treated animals but this relatively minor impairment may augur well for the use of systemic phthalocyanine administration in photodynamic therapy.